The production and the use of electronically conductive polymers are well known in the art. In DE-A-41 32 614 the production of film-forming, electronically conductive polymers by anodic oxidation of pyrroles, thiophenes, furans or aromatic amines (or their derivatives.) is effected with a sulphone compound present in the electrolyte solution. In U.S. Pat. No. 5,254,648 the preparation of electrically-conducting polythiophenes are described. In U.S. Pat. No. 5,236,627 a method for the preparation of polypyrrole is described. There are several uses for such polymers, they can be used as electrodes in capacitors, as disclosed in, e.g., EP-A-803 886, they are useful as a replacement for metal conductors in electrostatic discharge elimination and electromagnetic shielding as disclosed in, e.g., WO-A-96/266355. The layers of electrically-conductive polymers can be shaped into "wires" or channels using conventional photolithographic techniques and can then be used as interconnects for microchip fabrication, in devices requiring controlled resistance of resistive "channels", in non-linear optics, etc. Such shaping of electrically-conductive polymers into "wires" or channels has been disclosed in U.S. Pat. No. 5,561,030. Also in WO-A-97/18944 methods for patterning electrically-conductive polymer layers are disclosed.
Many of the electrically conductive polymers can not be applied to an object from an aqueous solution but have to be applied from a composition with organic solvents, e.g. polyaniline is frequently processed from solutions in cresol. In the light of ecological needs, the need to use organic solvents is a drawback and can hamper the widespread use of electrically conductive polymers. In EP-A-440 957 a method for preparing polythiophene in an aqueous environment and applying polythiophene from an aqueous solution has been described. Such a solution is up until now mostly be used in photographic materials as disclosed in, e.g., U.S. Pat. Nos. 5,312,681, 5,354,613 and 5,391,472.
An other limiting factor in the use of electrically-conducting polymers is the fact that, when the polymer is applied in an amount leading to good conductivity, the layers are frequently coloured, which is undesired when these polymer layers are to be used as transparent electrode in LCD or electroluminescent devices. Therefore much efforts have be done to increase the conductivity of the polymers without increasing the coloration so that thin, almost colourless layers of electrically-conductive polymers can be applied having high conductivity.
In EP-A-686 662 it has been disclosed that layers of polythiophene coated from an aqueous composition could be made with high conductivity. Therefore the aqueous composition of the polythiophene comprises further a di- or polyhydroxy compound and after coating said composition and drying the layer, the layer has to be treated at temperatures between 150 and 250.degree. C. in a separate production step. Although the layers disclosed in EP-A-686 662 have a low resistivity of about 300 .OMEGA./square and lower, there is still a need for a method wherein the low resistivity can be reached at lower temperature and without the need of a separate annealing step.